1. Field of the Invention
The present invention relates to a vehicle bumper assembly to be connected to a vehicle body member via a support bracket attached to a bumper.
2. Prior Art
Vehicle bumper assemblies that are connected to a vehicle body member via a support bracket attached to a bumper are common. Examples of this kind of bumper are shown in U.S. Pat. Nos. 3,511,345B1, 4,995,660B1, 6,174,009B1, 6,231,095B1, EP1114753A2, DE10002148A1, etc.
U.S. Pat. No. 3,511,345B1 discloses a vehicle bumper assembly comprising a bumper connected to a vehicle body member via a tubular support bracket having two or more axially aligned tubes of different diameters that bring about impact absorption.
U.S. Pat. No. 4,995,660B1 discloses a vehicle bumper assembly using a cylinder as a support bracket to bring about impact absorption.
U.S. Pat. No. 6,174,009B1 discloses a vehicle bumper assembly connecting a tower to be crushed by joining a support bracket and a bumper using a swivel connection.
U.S. Pat. No. 6,231,095B1 discloses a vehicle bumper assembly having a bumper connected to a vehicle body member using a support bracket with one split end of a tube flared and welded to a vehicle body frame.
EP1114753A2 discloses a vehicle bumper assembly having a bumper connected to a vehicle body member using a support bracket provided with a large number of depressions on the surface of a tube carrying out impact absorption.
DE10002148A1 discloses a vehicle bumper assembly having a bumper connected to a vehicle body member using a support bracket utilizing an extension of a spring, that is normally folded.
Although prior vehicle bumper assemblies have the same characteristic feature that a support bracket has the ability to absorb impacts, the support members that bring about such impact absorption have a wide variety of configurations. This is due to the fact that (1) a superior ability to absorb impacts, (2) a strong connection between a bumper, a support bracket and a vehicle body member, and (3) reliable impact absorption (reliability) are demanded of a vehicle bumper assembly. In addition, since attachment space for a support bracket is limited, (4) space-saving and (5) a simple configuration are also demanded. Therefore, investigations have been carried out in order to develop a vehicle bumper assembly using a support bracket meeting the requirements in (1) to (5) above in a balanced manner and having the ability to absorb impacts by utilizing plastic deformation.
A vehicle bumper assembly comprises: a bumper; a bumper connection member attached to the bumper; a support bracket attached to the bumper via the bumper connection member, the support bracket being in the form of a molded multi-step tubular structure having a plurality of plastically deformable straight tube portions of different outer diameters contiguous to one another, the tube portions being formed by reducing and enlarging an initially-uniform-diameter blank tube radially at longitudinally spaced local positions; and a vehicle body member connected to the support bracket via a vehicle body connection member; wherein one end tube portion of the support bracket being connected to the bumper via the bumper connection member, and the other end tube portion of the support bracket being connected to the vehicle body member via the vehicle body connection member; the bumper connection member being installed to one end or one end portion of the bumper by utilizing bolts or rivets or welding; the bumper connection member having a connection hole on the surface thereof opening toward the direction to the vehicle body member; and the one end tube portion of the support bracket being inserted into the connection hole of the bumper connection member and having a side surface welded to a peripheral edge of the connection hole.
The bumper has at the position toward the one end and in a surface facing the vehicle body member a cutaway, and said bumper connection member is attached to said cutaway of the bumper. In this case, only the rear surface of the bumper or large portion of the end portion of the bumper including the rear surface may be cut away. The case of the entire end portion of the bumper being cut away is when the bumper connection member is attached to a bumper with both ends pre-cut so as to be rectangular. The tube portion at one end of the support bracket connected to the bumper is configured so that the periphery of one end of the tube portion is pressed against the inner side of the front surface of the bumper connection member, and an impact received by the bumper is made to travel in the direction of the contiguous tube portions of the support bracket via the bumper connection member. In this way, the present invention is characterized by individual connection members connecting the support bracket, fulfilling the plastic deformation requirements of (1), and the requirements (4) and (5) due to being a single unit, to the bumper and the vehicle body member in a simple and secure manner.
When a tube portion at a small outer diameter (hereinafter referred to as a small tube portion) sinks into a tube portion with a large outer diameter (hereinafter referred to as a large tube portion) by a collosion, plastic deformation is caused in the area of the support bracket used in the present invention between a step of both tube portions and the large tube portion. Individual connection members attached to the front and back of the support bracket therefore do not interfere with plastic deformation of the support bracket. When the tube constituting the support bracket has a three step structure, although a sequence of a large tube portionxe2x80x94a small tube portionxe2x80x94a large tube portion (the diameters of the first and the last large tube portions may be different) or a small tube portionxe2x80x94a large tube portionxe2x80x94a small tube portion (the diameters of the first and the last small tube portions may be different) can be considered, a multi-step structure having contiguous tube portions according to a size of outer diameters (namely a small tube portionxe2x80x94a middle tube portionxe2x80x94a large tube portion) is preferable. In this case, it is preferable to have a relationship where the outer diameter of the small tube portion is narrower than the inner diameter of the middle tube portion, and the outer diameter of the middle tube portion is narrower than the inner diameter of the large tube portion.
The bumper connection member is preferably configured to provide a cylindrical wall so as to project from a peripheral edge of the connection hole contacting the side surface of the tube portion, and to weld the peripheral edge of the cylindrical wall and the side surface of the tube portion. The cylindrical wall can be provided together with the connection hole using a burring process. Welding using the cylindrical wall makes the welding operation straightforward and suppresses detachment of the welded joint portion of the support bracket starting plastic deformation and the bumper connection member so as to fulfill requirements (2) and (3). The projecting direction of the cylindrical wall maybe backward or forward, however, a direction where an impact is applied, or a direction facing the vehicle body member (backward) is usually preferable. The connection hole is configured so that the periphery of one end of the tube is pressed against the inner side of the front surface of the bumper, and an impact received by the bumper is made to directly travel in the direction of the contiguous tube portions of the support bracket.
The vehicle body connection member is preferably formed by causing an annular ridge to abut against the end periphery of the tube of the support member end and welding, and the annular ridge has an opening, as a crumple containment hole, having a support surface, enclosed by an outer periphery that is wider than the outer diameter of the tube at the support member end and an inner periphery that is narrower than the inner diameter of a tube connected to the tube at the support member end, and the support surface inner side. This vehicle body connection member assures stable plastic deformation of the support bracket when applied to a three- or more-step support brackets. For example, xe2x80x9can one-end tube portion at one end of the support bracketxe2x80x9d will be the large tube portion, and xe2x80x9ca tube portion contiguous to this one-end tube portionxe2x80x9d will be the middle tube portion when the support bracket is a three-step structure of the small tube portionxe2x80x94the middle tube portionxe2x80x94the large tube portion. In addition, the size of the deformed-tube receiving hole is defined from the range where the outer diameter of the small tube portion less than the diameter of the deformed-tube receiving hole less than the inner diameter of the middle tube portion (=the diameter of the inner periphery of the annular ridge), considering the plastic deformation portion starting from the step so as to allow a small tube portion to sink in.
The support surface that the annular ridge has supports the approaching step between the large tube portion and the middle tube portion caused by plastic deformation due to impact absorption, so that plastic deformation does not occur at the peripheral edge of the large tube portion. As a result, detachment of the peripheral edge of the large tube portion can be prevented when the support bracket is absorbing an impact, which fulfils the requirements (2) and (3). The small tube portion can be sank through the inside of the annular ridge due to plastic deformation since the deformed tube receiving hole is opened inside of the inner periphery of the support surface. This movement makes the plastic deformation range larger, and therefore fulfills requirement (1).